1. Field of the Invention
The present invention relates to an image processing apparatus incorporated in a digital copying machine or a scanner and the like. More particularly, the present invention relates to an image processing apparatus that executes image processing such that, in the case where a storage capacity is short while image information is compressed and stored, a compression rate is improved.
2. Description of Related Art
Conventionally, there is well known an image processing apparatus capable of compressing image data acquired by reading a document for a plurality of pages, storing the compressed data in a memory or the like, and repeatedly reading out the stored data. Such an image processing apparatus is incorporated in a digital copying machine or the like. The memory in the image processing apparatus is limited in capacity, and thus, image data on the entire document has not been always stored therein. Thus, in the image processing apparatus, countermeasures against a case in which a memory capacity shortage occurs are taken. One of such countermeasures is disclosed in Japanese Patent Application Laid-open No. 10-224579. In this countermeasure, if a memory capacity shortage occurs, reading of the document is temporarily interrupted, and image data already stored in a memory is read out and printed. Then, after a sufficient memory capacity has been allocated, the reading of the remaining document is restarted.
However, in an invention disclosed in Japanese Patent Application Laid-open No. 10-224579, there has been a problem that processing functions such as electrical sorting for electrically sorting image data or copy mode processing called booklet creation is canceled. This is because it is required to store the image data on the entire document in a memory in order to execute these processing functions. That is, if a memory capacity shortage occurs, the image data on the entire document cannot be stored, and these processing functions are canceled.